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LED Yo-Yo Side Caps 


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LED Yo-Yo Side Caps 

Written By: Eric Chu 


Caliper (1) 

Drill (1) 

Needlenose pliers (1) 


Sandpaper (1) 

Straightedge (1) 

X-Acto Compass Cutter (1) 


There aren't many low-budget ways to customize one's yo-yo. The most common ones are 
either painting or dyeing, but they're limited: paint chips off with time, and dyeing is only for 
plastic yo-yos. 

Being a yo-yo fanatic, I regularly visit the blog for yo-yo news. There I 
recently read a post about spin-activated LED side caps that fit into the side of yo-yos. They 
are low-cost ($6) and look very cool; a perfect customizing add-on for any yo-yo. 
Unfortunately, they only come in one size, thus only fitting a few yo-yos. I thought it'd be a 
fun project to make my own set (and it was!). Here's my guide to making your own. I used a 
One Drop Project yo-yo because it has a nice flat hub that leaves plenty of room for side 

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How It Works 

caps, but you can use pretty much any yo-yo that's got concave sides. 

How It Works 

Using the centrifugal force generated by the spinning of the yo-yo, the spring, acting as the 
switch, is pulled outward. It makes contact with the positive leads of the LEDs, thus 
completing the circuit, turning the LEDs on. 

• Measure the inner diameter of your 
yo-yo with a pair of calipers as 

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How It Works 

12 3 4 IMP 8 9 10 11 \2 \3> U A5 

• Now divide the diameter by 2 to get 
the inner radius. 

• Slide the caliper to this number and 
set the compass cutter to align with 
the tips of the caliper. 

• Tighten the knob on the cutter to 
lock the cutter in place. 

• Take your plastic sheet and use 
the compass cutter to cut out the 
side cap. 

• Test the cap to see if it will fit into 
the yo-yo. 

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How It Works 

Measure the diameter of your lithium battery, divide it by 2 to get the radius, and set the 
position of the compass cutter to it. 

Lightly mark the circumference of 
the battery onto the cap. We will 
use this to center the battery later. 

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How It Works 

• Loosen the compass cutter and set 
it so that the blade is between the 
circumference of the cap and 
battery mark. 

• Lock it back up and make two light 
marks across from each other. 
These are for positioning the LEDs. 

Step 7 

• Use a pen to mark the center 
points for drilling the holes for the 

• Use a straight-edge and align it to 
the center point of the cap. 

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How It Works 

• Drill out the #9 holes on your cap. 

• The #9 drill bit makes holes into 
which 5mm LEDs can be press- 

Insert LEDs into holes "bulb" first. 
Make sure the longer (positive) 
leads are both facing the same 
direction and the shorter (negative) 
leads as well. 

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How It Works 

Step 10 

• Bend the negative leads to match 
the picture. Make sure they are in 
contact with each other. 

• Notice that the leads are passing 
through the area where the battery 
will sit. 

Step 11 

• Apply hot glue to the cap in two places as shown in the picture and press the negative side 
of your battery onto the glue, making sure the negative leads touch the negative side of the 

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How It Works 

Step 12 — Make your spring 

• First strip the enamel coating off 
your magnet wire by folding a piece 
of sand paper in half with the grit 
facing in and running about 3 
inches of wire between the grit. 

• Sand the wire until you see the 
bare copper. Make sure not to sand 
too much or else the wire will 

• Then tightly wrap the wire around a 
small round tube such as the ink 
cartridge of a ball point pen, a 
small screwdriver, etc. 

• Wrap wire 5 times around and cut 
off the spring. 

Step 13 

• Bend the positive leads to match 
the picture. Make sure to have 
enough room for your spring. 

• Cut a piece of aluminum insulation 
tape and wrap it around both leads. 

• Tape your spring down with 
aluminum tape. 

• Adjust the spring to sit as close as 
possible to the positive leads but 
without touching them. Pliers come 
in handy. 

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How It Works 

Step 14 

Tape on a piece of double-sided tape onto the battery, stick it to your yo-yo and you're 

Step 15 

• You're done! Try out your yo-yo 
and see if the LEDs light up. 

■ Troubleshooting 

• LEDs are not turning on when I 
throw my yo-yo. 

• Move the spring close to the 
positive leads. Check the 
polarity of the LEDs (+ to + and 

• LEDs stay on after use. 

• Move the spring slightly farther 
back, away from the positive 


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How It Works 

If the LEDs are not turning on when you throw your yo-yo, move the spring close to the positive 
leads. Also, check the polarity of the LEDs (+ to + and - to -). 

If the LEDs stay on after use, move the spring slightly farther back, away from the positive 

This project first appeared in MAKE Volume 22 . page 113. 

This document was last generated on 201 2-1 1-03 01 :1 1 :36 AM. 

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